The present invention concerns the handling and disposal of hazardous wastes and, more specifically, containers in which such wastes can be transported and stored.
Hazardous wastes are substances which are usually unwanted byproducts of industrial processes, and are a present or potential danger to the health of humans or other living organisms because they exhibit undesirable properties such as toxicity, carcinogenicity, nondegradability, biological magnification, or the like. Under present technology, a wide variety of useful products cannot be manufactured without also producing some hazardous wastes. It is not presently possible to recycle all of the wastes, so safe means of disposal must be found.
As awareness of the dangers of air and water pollution has increased, methods of disposing of wastes into the air (through burning, for example) and in rivers or oceans have been recognized as being undesirable in many situations. Legislation and regulations strictly limit such disposal methods in the United States and in many other countries.
As disposal of hazardous wastes into the air and water has been reduced, there naturally has been an increase in the amounts disposed of on land. One landbased method is to dig a pit in the ground and merely dump the wastes into it. Another method is to bury the wastes in a landfill.
In many land-based disposal methods, preventing the wastes from contaminating the ground water supply is a major concern. In landfills, this problem is often addressed by excavating the landfill pit in soil that is naturally rich in clay, a substance which is relatively impermeable to water, and then adding an additional layer of compacted clay on top of the excavated surface. A layer of gravel is often placed on top of the compacted clay. Government regulations sometimes require an additional artificial lining layer on top of the compacted clay and gravel. Wastes to be buried in the landfill are usually solidified, if they are originally liquid, by adding a bulking agent such as kiln dust, fly ash, or lime (all of which have hydrating characteristics). The solidified waste is then dumped in the bottom of the landfill, and covered with a material that will help seal the waste from the elements, thus forming a waste "cell". This process is repeated each day so the landfill gradually fills up with cells of covered waste, each covered with an individual clay cap when full. When the landfill is completely full, a final cover, which might be a two foot thick layer of clay, is placed over the top. Grass might be planted on top to help control erosion.
The success of the clay and artificial liners in preventing leaching of the wastes from the landfill into the surrounding ground water must be monitored. One way of doing so is to build a sump at the bottom of the gravel layer. A pipe or tube can be used to connect this sump to the surface, so the nature of the liquid in the sump can be tested periodically. Another way is to drill water sampling wells at several points around the landfill. If hazardous substances can be detected in the water taken from these wells, the wastes may be leaking from the landfill.
Some landfills or pits are located adjacent to or within the confines of plants that generate hazardous wastes. However, many disposal areas are at remote locations, so the waste must be transported from the point of generation to the point of disposal. The dangers of exposure to the waste require that strict precautions be taken when it is shipped. For example, the container in which it is shipped must be strong enough to prevent leakage. If the waste containers are to be shipped on the highways, they should be able to withstand the stress exerted by a collision between the truck which is carrying them and another vehicle.
As public awareness of hazardous waste has increased, efforts have begun to clean up unsatisfactory dump sites. The "Superfund" legislation in the United States is one example of such a program. Hundreds of hazardous waste sites have already been identified in the United States in which waste is not now safely stored. Many of these sites will be cleaned up by transferring the waste to new disposal sites which meet current regulations. Thus, the Superfund and other similar cleanup programs involve two potentially troublesome aspects of hazardous waste handling: transportation and disposal. Of course, industrial sources continue to generate hazardous waste daily, and much of it must also be transported to disposal sites.
At the same time, increased public and scientific concern about hazardous waste has drastically slowed the opening of new landfills. Proposing the opening of a new site raises difficult political as well as technological questions, which are often addressed in regulatory proceedings that can last for years. Therefore, at a time when the demand for environmentally sound disposal facilities is large, the supply of such facilities has been sharply limited. Any procedure that would permit the reuse of existing sites would be a tremendous benefit. The present invention is an improvement in hazardous waste technology which can help solve some of the problems of both transportation and disposal, and can give the public greater confidence in the safety of those operations.